Throughout the world, there are many different types of industrial water systems. Industrial water systems exist at least in part so that necessary chemical, mechanical, and biological processes can be conducted to reach their desired outcomes. Even the best water treatment programs currently available cannot always prevent fouling in industrial water systems. If an industrial water system is not periodically cleaned to remove contaminants, the industrial water system will almost certainly become heavily fouled.
Fouling has a negative impact on the industrial water system. For example, severe mineral scale (i.e., inorganic material) can build on the water contact surfaces. Scale on an industrial water system surface presents an ideal environment for the growth of microorganisms. The presence of microorganisms poses an additional challenge to water treatment of the industrial water system, as biocides, scale inhibitors, and/or corrosion inhibitors may be necessary to maintain efficient operation of the industrial water system.
Evaporative cooling water systems are particularly prone to fouling, which can occur via a variety of mechanisms. Non-limiting examples of fouling mechanisms include deposition of airborne, water-borne, water-formed, and/or microbiological contaminants; water stagnation; process leaks; and other factors. If fouling is allowed to progress, the industrial water system can suffer from decreased operational efficiency, equipment failure, lack of water quality control, and increased health-related risks associated with microbial fouling.
As previously mentioned, microbiological contaminants may cause fouling. Non-limiting sources of microbiological (i.e., microbial) contamination are airborne contamination, makeup water, process leaks, and improperly cleaned process equipment. These microbials can establish colonies on any wettable or even semi-wettable surface of the industrial water system. Once microbial counts are present in the bulk water, within a short period of time, more than 99% of the microbes present in the water will be present on all surfaces within biofilms.
By design, cooling towers are excellent air scrubbers. As a consequence of the cooling process, a cooling tower typically flushes airborne contaminants into the water phase. These contaminants can ultimately find their way to the heat exchanger surfaces, where they become deposited, thereby reducing heat transfer. Non-limiting examples of such contaminants include particulate matter, organic and inorganic contaminants, oils, process contaminants, microorganisms, and so forth. Suspended matter in the cooling water provides the microorganisms with readily available nourishment for sustaining life and reproduction. It is well established that the presence of inorganic, organic, and microbiological deposits have a detrimental impact on the operational parameters of an industrial cooling system, resulting in reduced efficiency and increased operating cost.
A filtration system can be used to at least partially remove particulate contaminants and prevent them from reaching concentrations that can adversely impact efficient cooling system operation. The filtration system may be a full-flow in line system or a partial flow side stream system. The side stream configuration provides particular advantages to the full flow system, such as allowing for a smaller filtration unit and the ability to service off-line while not affecting the cooling process. Generally, the side stream configuration only draws between 2 and 10 percent of the flow as compared to the overall circulation of the cooling system.
Any or a combination of several different types of filters may be utilized for the purpose of filtration, and their use depends on the nature of the water and the level of purification wishing to be attained. Non-limiting examples include sand filters, cartridge filters, screen filters, and membrane filters, which may employ ultrafiltration, microfiltration, reverse osmosis, and forward osmosis. Typically in a filtration system, the water to be cleaned wets and passes through the entire filtration surface, with cleaner water leaving the filtration system as filtrate. When sufficient dirt has collected on the filtration surface, the filtration surface should be cleaned, thereby restoring performance. Methods of cleaning the filtration surface depend on the design of the filtration device. For example, a cartridge filter is not typically cleaned but instead replaced. However, a sand or screen filter will typically undergo a manual or automated backwash cycle to remove the collected contaminants. For membrane filters, there may be similar chemical or non-chemical based cleaning processes, depending on their design.